1. Field
The present invention relates to electronics and, more specifically but not exclusively, to Doherty amplifiers.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
A Doherty amplifier has a main amplifier branch and one or more peak amplifier branches that are designed to enable the amplifier to provide high-power amplification by supplementing the amplification provided by the main branch during peak power operations. During normal power operations, the peak branches may be disabled such that high-efficiency amplification is provided by only the main branch. Doherty amplifiers are used in high-capacity wireless systems having modulated signals that exhibit high peak-to-average power ratios.
Certain conventional design practices for Doherty amplifiers rely on Class-AB load-pull data and/or non-linear models in circuit simulators to characterize active devices. The design process is mainly based on manual calculations derived from Doherty design principles and limited load-pull data. Designers make many assumptions such as what input power split to use, which impedance modulation ratio to use, and which gain and compression values to use for each device. Such assumptions might not be accurate and may cause large discrepancies between expected and achieved performance characteristics of the resulting Doherty amplifier, leading to missed milestone deadlines and lower performance capabilities of the amplifier. The deviations from the desired performance are discovered only after the first prototypes are built and tested, at which point it is usually too late to make major changes to fix problems caused by faulty assumptions. Deviations that can be fixed involve manual tuning on the bench, which is a costly, time-consuming, and laborious process with no guarantees of success. Since the tuning is done on a small sample of prototypes, there is no guarantee that the solution will be optimal for large-scale production.